Yes but if they are past prime you don't critic their losses as much, it's all circumstantial.
For example no-one even cares to mention Ali's losses to Holmes or Berbick when ranking him but, if you take a fighter like Lennox Lewis who was pretty past it when he beat Vitali, he gets a lot more credit for that.

It's not just a case of who has the best names on their resume which is why it's so hard to compile a well thought out list. Only the best historians can make a list which truly represents their opinions as a lot of work needs to go into it. It's something I haven't done, and probably will not do.